The present invention relates to a method for sealing a light emitting element using a gel sealant made by causing a gel precursor to gel to lose liquidity, and further relates to a light emitting element module formed by this method.
The light emitting element module, such as a light emitting diode (LED) or the like, has properties such as having low power consumption, being miniature, being lightweight, and the like, and is used as a light source of a printer head, a light source of a liquid crystal backlight, a light source of various types of meters, and the like.
As an example of such a light emitting element module, as shown in FIG. 7, there is a light emitting element module containing a light emitting element 90, a base 91 having a concave portion in which the light emitting element 90 is stored, a lid 92 covering the light emitting element 90, and a silicone gel 93, for sealing the light emitting element 90, disposed between the base 91 and the lid 92.
The silicone gel 93 for sealing the light emitting element 90 gels by mixing two types of liquids and applying heat thereto. The gelling reaction of the two types of liquids is achieved by applying heat of 80 degrees Celsius to 150 degrees Celsius, thereby forming the silicone gel 93.
One method for sealing the light emitting element involves placing the light emitting element 90 on the base 91, thereafter unifying the lid 92 and the base 91, and, as shown in FIG. 7, mixing and injecting the two types of liquids making up the silicone gel 93 into between the lid 92 and the base 91 using an injector 94, and then heating the liquids. At this time, the mixture of the two types of liquids is injected until overflowing, so that air bubbles causing a decrease in light output or the like are not mixed in.
Furthermore, there is another method for sealing the light emitting element upon storing the light emitting element in the concave portion of the base, injecting the soft material thereon, placing on the soft material the lid protruding in a direction of the light emitting element, and thereafter applying heat thereto to unify the lid, the soft material, and the base (see, e.g., Patent Document 1). The soft material is injected through potting, and thus is fluidic, but the heat applied after the lid is placed causes the soft material to gel.                Patent Document 1: Japanese Unexamined Patent Application Publication No. 2003-318448        
Through the method for mixing two types of liquids while injecting the mixture with the injector 94, however, the liquid must be injected until overflowing to prevent air bubbles between the base 91 and the lid 92. In other words, the overflowing liquid is wasted. The method raises another problem that it is difficult to align a tip of the injector 94 with injection entrance for injecting the two types of liquids between the base 91 and the lid 92.
Furthermore, heating is necessary for the two types of liquid that become the silicone gel 93 to gel. In other words, it is necessary to use a material for the base 91, the lid 92, and the like that can withstand the heat required to cause the two types of liquids to gel, thereby limiting the material that can be used. Furthermore, through such a method, a substance using a solvent cannot be used as the gel precursor of the gel because such a solvent causes air bubbles when evaporated, thereby decreasing the light output.
On the other hand, in the method for sealing the light emitting element of Patent Document 1, by placing the lid that protrudes in a direction of the light emitting element, air bubbles can be prevented from arising in the fluidic soft material. Determining a location at a time when the viscous soft material is injected thereby becomes relatively easy. The method of Patent Document 1, however, requires heat to cause the soft material to gel and does not allow the use of a solvent for the gel precursor of the soft material, thus leaving unsolved problems.